You do. I lived in Vienna for two years, for example, without needing a car for that whole time. So, that is relative. I could simple argue that you should simply learn to live without cars because their are too dangerous given the number of people that are killed "by cars" every day.
But this would be my opinion, it wouldn't be right to force you not to have a car simply based on my personal opinion, even though you might kill someone innocent with that car someday.
You don't. In my opinion, I need one. And just as in the car case, where my opinion is not more important than yours, in this case, your opinion is not more important than mine too.
We do, but I might think that they're not enough. Because I might argue that a car going at 40 mph can easily kill someone. But you wouldn't like that restriction, even though it could save many lives. Just as I wouldn't( and I don't, since I live in communist Brazil) like restrictions in the types of guns I can buy or the number of bullets I can carry.
It's is always a matter of considering that one's opinion is not more important than the other's, because this is a complicated world with very different people. And what should or should not be restricted will always be very subjective in each mind. So it is best to just live our lives the way we want to and not try to dictate the way others should to live. Especially given that there is no life without risk in this world, be it driving a car or carrying a gun.